Well now!
Try to sit beside a pianist playing nice calm music on the piano, you will guaranted never hear anything coming from blacknes. The sound comes from the piano, which is never really silent, and from yours and his breathing, heartbeat and moves.
And when recorded simply and nonprocessed and played back, the same should be the case. But electronics do have certain selfnoise, but that can easily be listened down through. The point about the blackness is actually, that most of the selfnoise goes away together with all signals below it, and that because of capacities present at the output of the amplifier, either as cable capacitance or as output device capacitance. This is a law of nature, since any capacitor has to be charged before any conductance is present.
You can experience this phenomenon taken to the extreme i.e. Linsley Hood´s class A amp or i.e. the british made Sudgen single ended class A amps.
They all feature a large capacitor in the output, because of their single ended design.
Btw. when dynamics is taken to the extreme, i.e. 100 dB or so, there will never be any quietnes present at all. Try to put on a track attenuated i.e. -80dB, you will hardly hear anything, unless you hold your breath or turn your volume up way beyound the normal 0dB FS clipping point.
The black background is simply a trick invented to make one believe the dynamics are extended, when they are not. It is induced by gear, and it also is a non fidelity characteristic, which just happen to have been modern at a time.
Used with tube gear they might prove useable, because output transformers always suffers from hysteresis, which takes away low level information anyway, and the selfnoise is somewhat higher than on SS gear, but I did never try this out.